This invention relates to batteries.
Batteries, such as alkaline batteries, are commonly used as energy sources. Generally, alkaline batteries have a cathode, an anode, a separator and an alkaline electrolyte solution. The cathode can include a cathode material (e.g., nickel oxyhydroxide), carbon particles that enhance the conductivity of the cathode, and a binder. The anode can be formed of a gel including zinc particles. The separator is disposed between the cathode and the anode. The alkaline electrolyte solution, which is dispersed throughout the battery, can be a hydroxide solution such as potassium hydroxide.
Undesirable capacity loss in batteries can be caused by corrosion of battery cans and/or self-discharge of the anode or cathode. For example, in an alkaline battery containing a gelled zinc anode and a nickel oxyhydroxide cathode, self-discharge at the anode can involve reduction of water (which leads to hydrogen gas evolution) and at the cathode can involve oxidation of water (which leads to oxygen gas evolution), respectively. These self-discharging reactions can greatly decrease cell discharge capacity, especially during storage. Having excellent capacity retention during storage can be an important feature of batteries, especially for primary batteries, which are not designed to be rechargeable.
An alkaline battery has a cathode containing a gold salt. Such an alkaline battery exhibits excellent high power performance, as well as excellent capacity retention, especially during storage, for example, at high temperature.
In one aspect, an alkaline battery includes a cathode containing nickel oxyhydroxide and a gold salt, an anode, a separator between the anode and the cathode, and an alkaline electrolyte. The anode includes zinc.
The nickel oxyhydroxide can include gamma-nickel oxyhydroxide (e.g., non-fractured spherical gamma-nickel oxyhydroxide). The nickel oxyhydroxide can include beta-nickel oxyhydroxide, which can include non-fractured spherical particles. The nickel oxyhydroxide can be cobalt oxyhydroxide-modified nickel oxyhydroxide (e.g., cobalt oxyhydroxide-coated gamma-nickel oxyhydroxide). The nickel oxyhydroxide can be derived from alpha-nickel hydroxide or beta-nickel hydroxide, which can include non-fractured spherical particles. The beta-nickel oxyhydroxide can be derived from a beta-nickel hydroxide precursor, which can include non-fractured, substantially spherical particles. The nickel hydroxide can be a cobalt hydroxide-modified nickel hydroxide (e.g., cobalt hydroxide-coated nickel hydroxide).
The gold salt can be gold (+3) oxide, gold (+3) sulfide, gold (+3) hydroxide, or gold (+3) acetate. The cathode can include less than 1000 ppm, for example, between 5 ppm and 1000 ppm, between 10 ppm and 200 ppm, or between 15 and 100 ppm, of a gold salt.
The cathode can include an oxidizing additive that is more strongly oxidizing than nickel oxyhydroxide. Examples of such an oxidizing additive include NaOCl, Na2S2O8, K2S2O8, KMnO4, BaMnO4, BaFeO4, AgMnO4 or AgO.
The cathode can be housed in a can coated on an inside surface with graphite, titanium nitride, titanium oxynitride, or gold. The coating can be a thin layer. The layer thickness can range from 5 to 25 microns.
The anode can include a gelling agent, zinc particles, and, optionally, minor amounts of other additives, such as a gassing inhibitor.
The alkaline battery can be a primary battery.
The capacity loss of the alkaline battery having a cathode including the gold salt can be less than 30%, less than 20%, or less than 10% after storing the battery at 60xc2x0 C. for 4 weeks.
In another aspect, a method of manufacturing an alkaline battery including a cathode containing nickel oxyhydroxide and a gold salt, an anode, a separator between the anode and the cathode, and an alkaline electrolyte includes obtaining the cathode, and assembling the cathode, the anode, and the separator between the cathode and the anode to form the alkaline battery. The cathode mixture includes nickel oxyhydroxide, a gold salt, conductive carbon and an alkaline electrolyte. The anode includes zinc. The cathode mixture can be prepared by adding an aqueous alkaline solution containing the alkaline electrolyte and a gold salt to an admixture of nickel oxyhydroxide and conductive carbon. The admixture can be prepared by dry mixing powders of nickel oxyhydroxide and conductive carbon.
Other features and advantages of the invention will be apparent from the description and drawings, and from the claims.